Recording
In February 1976, Fleetwood Mac convened at the Record Plant in Sausalito, California, with the engineers Ken Caillat and Richard Dashut. The three parties shared production duties, while the more technically adept Caillat was responsible for most of the engineering; he took a leave of absence from Wally Heider Studios in Los Angeles on the premise that Fleetwood Mac would eventually use their facilities. The set-up in Sausalito included several small recording rooms in a large, windowless, wooden building. Most band members complained about the studio and wanted to record at their homes, but Fleetwood did not allow any moves. Christine McVie and Nicks decided to live in two condominiums near the city's harbour, while the male contingent stayed at the studio's lodge in the adjacent hills. Recording occurred in a six-by-nine-metre (20 by 30 ft) room equipped with a 3M 24-track tape machine, a range of high-quality microphones, and an API mixing console with 550A equalisers; the latter were used to control frequency differences or a track's timbre. Although Caillat was impressed with the set-up, he felt that the room lacked ambience because of its "very dead speakers" and large amounts of soundproofing.
The record's working title in Sausalito was Yesterday's Gone. Buckingham took charge of the studio sessions to make "a pop album". According to Dashut, while Fleetwood and the McVies came from an improvisational blues rock background, the guitarist understood "the craft of record making". During the formative stages of compositions, Buckingham and Christine McVie played guitar and piano together to create the album's basic structures. The latter was the only classically trained musician in Fleetwood Mac, but both shared a similar sense of musicality. When the band jammed, Fleetwood often played his drum kit outside the studio's partition screen to better gauge Caillat's and Dashut's reactions to the music's groove. Baffles were placed around the drums and around John McVie, who played his bass guitar facing Fleetwood. Buckingham performed close to the rhythm section, while Christine McVie's keyboards were kept away from the drum kit. Caillat and Dashut spent about nine days working with a range of microphones and amplifiers to get a larger sound, before discovering they could adjust the sound effectively on the API mixing console.
As the studio sessions progressed, the band members' new intimate relationships that formed after various separations started to have a negative effect on Fleetwood Mac. The musicians did not meet or socialise after their daily work at the Record Plant. At the time, the hippie movement still affected Sausalito's culture and drugs were readily available. Open-ended budgets enabled the band and the engineers to become self-indulgent; sleepless nights and the extensive use of cocaine marked much of the album's production. Chris Stone, one of the Record Plant's owners, indicated in 1997 that Fleetwood Mac brought "excess at its most excessive" by taking over the studio for long and extremely expensive sessions; he stated, "The band would come in at 7 at night, have a big feast, party till 1 or 2 in the morning, and then when they were so whacked-out they couldn't do anything, they'd start recording".
Nicks has suggested that Fleetwood Mac created the best music when in the worst shape, while, according to Buckingham, the tensions between band members formed the recording process and led to "the whole being more than the sum of the parts". The couple's work became "bittersweet" after their final split, although Buckingham still had a skill for taking Nicks' tracks and "making them beautiful". The vocal harmonies between the duo and Christine McVie worked well and were captured using the best microphones available. Nicks' lyrical focus allowed the instrumentals in the songs that she wrote to be looser and more abstract. According to Dashut, all the recordings captured "emotion and feeling without a middle man ... or tempering". John McVie tended to clash with Buckingham about the make-up of songs, but both admit to achieving good outcomes. Christine McVie's "Songbird", which Caillat felt needed a concert hall's ambience, was recorded during an all-night session at Zellerbach Auditorium in Berkeley, across San Francisco Bay from Sausalito.
Following over two months in Sausalito, Fleetwood arranged a ten-day tour to give the band a break and get fan feedback. After the concerts, recording resumed at venues in Los Angeles, including Wally Heider Studios. Christine McVie and Nicks did not attend most of the sessions and took time off until they were needed to record any remaining vocals. The rest of Fleetwood Mac, with Caillat and Dashut, struggled to finalise the overdubbing and mixing of Rumours after the Sausalito tapes were damaged by repeated use during recording; the kick and snare drum audio tracks sounded "lifeless". A sell-out autumn tour of the US was cancelled to allow the completion of the album, whose scheduled release date of September 1976 was pushed back. A specialist was hired to rectify the Sausalito tapes using a vari-speed oscillator. Through a pair of headphones that played the damaged tapes in his left ear and the safety master recordings in his right, he converged their respective speeds aided by the timings provided by the snare and hi-hat audio tracks. The prolonged overdubbing process had also worn the 24-track master tape, leaving many of its sounds dull and flat by the time mixing began; engineers used the then-novel Aphex Aural Exciter, a harmonic enhancer, to restore some of the tape's lost top-end clarity. Fleetwood Mac and their co-producers wanted a "no-filler" final product, in which every track seemed a potential single. After the final mastering stage and hearing the songs back-to-back, the band members sensed they had recorded something "pretty powerful".
